1. Field of the Invention
The invention generally relates to multi-band/multi-mode power amplifiers and more particularly to multi-band/multi-mode power amplifiers that share hardware of the signal path.
2. Prior Art
Prior art multi-band/multi-mode (MB/MM) power amplifiers (PAs) use separate signal paths for each supported band. FIG. 1 shows such an exemplary prior art multi-band PA 100 having a low-band (LB) signal path 110 and a high-band (HB) signal path 120. It is usually the case that the bypass capacitors of the radio frequency (RF) signal path stages dominate the die area on which the PA is implemented. Having two separate signal paths results in a duplication of the bypass capacitors and thus requiring a much larger die area. If more than two signal paths are used then the hit grows proportionately.
Having separate signal paths results in duplication of circuits, such as, the bias circuits of each of the signal paths. Furthermore, the separate signal paths use frequency tuned stages that can usually cover only a single band, or at best few closely spaced bands, e.g., two adjacent bands. It would therefore be readily understood by those of ordinary skill in the art that the prior art suffers from several drawbacks with respect to MB/MM PAs, namely, increased die area and complexity, which in turn also impact the cost of the solution.
Therefore, in view of the deficiencies of the prior art, it would be advantageous to provide a solution that overcomes these deficiencies.